A data gathering device for recording driving data which provides verification of the details of an accident in order to settle the question of fault in an objective manner by reconstructing the movement path of the vehicle is acted upon by the measurement signals of its sensors which continuously detect the driving dynamics of the vehicle. This is effected substantially with two significantly different signal shapes.
In normal driving, predominantly low-frequency signals with relatively small signal amplitudes are detected. As a rule, these signals are recorded over a longer period of time, whereas an accident situation is characterized in that higher-frequency signals with a relatively large signal amplitude are available for recording for a short period of time, these signals generally being caused by a collision.
Data gathering devices of this type should be capable of recording as much data as possible. On the other hand, in a low-cost device suitable for use in vehicles and intended for multiple applications the storage capacity must be kept within an economically reasonable limit. Therefore, it is necessary to search for arrangements which provide a way of meeting these conflicting requirements.
It is known from EP-118 818 B1 that the measurement signals detected by an accident-data writing device by means of sensors are sensed in a fixed cycle and stored as driving data. However, a fixed clock frequency cannot meet the aforementioned requirements. An accident situation whose significant, analog measurement signals are generally only present for less than 1 second cannot be detected with sufficient accuracy by an individual clock frequency selected for normal driving, since the resolution, i.e. the number of measurement points which are stored, is too low. On the other hand, a constantly high sensing rate would result in a scarcely meaningful flood of data which would be difficult to manage.
One solution might be simply to increase the sensing rate by an appropriate degree at the occurrence of the accident. But this step has the considerable disadvantage that precisely the measurement signals of the initial phase of the accident cannot be detected with a high resolution because of the unavoidable response time for the jump in frequency resulting from the required period for detecting the accident event, the electronic signal transit times, and the build-up phase for the higher sensing frequency.